Power And Distribution Transformer Operation Regulations

Generally, when we use power and distribution transformer, we will be limited by many requirements. At this time, we need to understand the operation rules of power transformers to use more familiar applications. Let's take a look at them in detail below.

1. The basic requirements for the operation of power and distribution transformer (hereinafter referred to as transformers) and the requirements for the operation mode. It can be used for the basic requirements, operation mode, operation and maintenance, abnormal operation and treatment of power transformers (hereinafter referred to as transformers), as well as requirements for installation, maintenance, testing and acceptance.

2. Check the relevant national regulations for the implementation of standards.

3.1 Protection, measurement, cooling devices

3.1.1 The power and distribution transformer shall be equipped with protection and measurement devices in accordance with the relevant standards.

3.1.2 The safety protection device, cooling device, oil protection device, temperature measuring device, oil tank and accessories of the oil-immersed transformer body shall meet the requirements of GB6451. The relevant devices of the dry-type transformer shall meet the corresponding technical requirements.

3.1.3 When the transformer is protected by a fuse, the performance of the fuse must meet the requirements of the short-circuit capacity, sensitivity and selectivity of the system. When a graded insulation transformer is protected by a fuse, its neutral point must be directly grounded.

3.1.4 For oil-immersed transformers equipped with gas relays, if there is no rising slope, the top cover should have a rising slope of 1% to 1.5% along the direction of the gas relay during installation.

3.1.5 The cooling device of the transformer shall meet the following requirements:

a. Install all cooling devices as specified by the manufacturer;

b. The cooling system of strong oil circulation must have two independent working power sources and can switch automatically. When the working power supply fails, the standby power supply should be switched on in vain and sound and light signals should be issued;

c. The strong oil circulation transformer should send out sound and light signals when the faulty cooler is removed, and automatically (water-cooled can be manually) put into the standby cooler;

d. The auxiliary motors of fans, water pumps and oil pumps shall be protected from overload, short circuit and phase failure; there shall be devices for monitoring the rotation direction of the motor of the oil pump;

e. The oil pump of the water cooler should be installed on the oil inlet side of the cooler, and ensure that the oil pressure in the cooler is greater than the water pressure by about 0.05MPa in any case (unless otherwise specified by the manufacturer). There should be a drain cock on the water outlet side of the cooler;

f. For transformers cooled by strong oil circulating water, the outlet of the submersible oil pump of each cooler shall be equipped with a check valve;

g. Transformers cooled by strong oil circulation should be able to control the switching of the cooler according to temperature and (or) load.

3.1.6 Power and distribution transformer should be equipped with temperature measuring devices according to the following regulations: DL/T572-95

a. There should be a thermometer for measuring the oil temperature of the top layer (the transformer on the column may not be installed), and the transformer in the unattended substation should be equipped with a thermometer indicating the higher value of the oil temperature on the top layer;

b. For oil-immersed transformers of 1000kVA and above, oil-immersed transformers of 800kVA and above, and dry-type factory transformers of 630kVA and above, the signal thermometer should be connected to the remote signal;

c. Transformers of 8000kVA and above should be equipped with remote temperature measuring devices;

d. Transformers cooled by strong oil circulating water should be equipped with temperature measuring devices at the inlet and outlet of the cooler;

e. When measuring temperature, the thermometer tube base should be filled with transformer oil;

f. Dry-type transformers shall be equipped with temperature measuring devices according to the manufacturer's regulations.

3.1.7 For transformers of 20000kVA and above in unattended substations, devices for remote monitoring of load current and top oil temperature shall be installed. For transformers cooled by strong oil circulation installed in unattended substations, reliable measures should be taken to ensure that the temperature of the transformer does not exceed the specified value when the cooling system loses power, and it should be included in the on-site regulations.

3.2 Other requirements for transformer operation

3.2.1 Large and medium-sized transformers should have temporary bell hoisting facilities and required work sites.

3.2.2 The installation of the pressure relief device shall ensure that the accidental fuel injection is unobstructed, and shall not be sprayed into the cable trench, busbar and other equipment, and shall be shielded if necessary.

3.2.3 The transformer should have a nameplate and indicate the operation number and phase mark. The distribution transformers installed in the transformer room or on the platform or on the column should also be numbered and hung with warning signs.

3.2.4 When the transformer is in operation, it should be able to safely check the oil level of the oil conservator and the bushing, the oil temperature of the top layer, the gas relay, and be able to take gas samples safely. If necessary, a fixed ladder should be installed.

3.2.5 The transformer installed in the room (hole) should have sufficient ventilation to avoid the temperature of the transformer being too high. Transformer room equipped with mechanical ventilation device should be able to send out remote signal when the mechanical ventilation is stopped. The ventilation system of the transformer should generally not be connected to other ventilation systems.

3.2.6 The door of the transformer room shall be made of flame retardant or non-combustible material and shall be locked. The name and operation number of the transformer should be marked on the door, and a stop, high voltage danger sign should be hung outside the door.

3.2.7 The site where oil-immersed power transformers are installed shall be provided with fire-fighting facilities and accident oil storage facilities in accordance with the relevant design regulations, and shall be kept in good condition.

3.2.8 For transformers installed in areas with a magnitude of seven and above, the following anti-vibration measures should be considered:

a. Fix the transformer chassis on the track;

b. When connecting the transformer bushing with the soft wire, it should be loosened properly; when connecting with the hard wire, the transitional soft connection should be lengthened appropriately;

c. When the cooler and the transformer are arranged separately, the transformer shall be connected with the cooler through valves, flexible joints and connecting pipes;

d. Transformers should be equipped with shock-proof gas relays;

e. The chassis of the transformer on the column should be fixed with the bracket, and the upper part should be fastened to the column. 3.2.9 When the actual short-circuit apparent capacity of the system where the transformer is located is greater than the value specified in Table 2 of GB1094.5, measures to limit the short-circuit current should be taken for the transformer in operation. The time of transformer protection action should be less than the duration of short-circuit heat resistance. 3.2.10 If an on-line monitoring device reflecting the insulation condition is installed on the transformer, its electrical signal shall be collected by the sensor and shall be reliably grounded. The device for collecting dissolved gas samples in oil should have good sealing performance. 3.3 Technical documents

3.3.1 Before the transformer is put into operation, the construction unit shall hand over the following technical documents and drawings to the operation unit.

3.3.1.1 After the installation of new equipment is completed, it is required to submit:

a. Instructions, drawings and factory test reports provided by the manufacturer;

b. The handover test report of the main body, cooling device and accessories (casing, transformer, tap changer, gas relay, pressure relief valve and instrument, etc.) during installation, inspection and handling records of the body during lifting inspection, etc.;

c. The whole process of installation (according to GBJ148 and the relevant regulations of the manufacturer) is recorded

d. The as-built drawings of the transformer cooling system, the control and protection circuit of the on-load voltage regulator;

e. Oil quality test and chromatographic analysis records;

f. Spare parts list.

3.3.1.2 After the overhaul is completed, it needs to be handed over:

a. The reasons for the overhaul of transformers and ancillary equipment and records of the entire overhaul process;

b. Test records of transformers and ancillary equipment;

c. Transformer drying records;

d. Transformer oil test, chromatographic analysis, oil treatment records.

3.3.2 Each transformer shall have the following technical files:

a. Transformer resume card;

b. All documents handed over after installation is completed;

c. Documents handed over after overhaul;

d. Prophylactic test records;

e. Calibration records of transformer protection and measuring devices;

f. Oil handling and refueling records;

g. Other test records and inspection records;

h. Transformer accident and abnormal operation (such as overtemperature, gas relay action, outlet short circuit, serious overcurrent, etc.) records.

3.3.3 When the transformer is handed over to an external unit, the technical files of the transformer must be handed over together.

4.

4.1 General operating conditions

4.1.1 The operating voltage of the transformer should generally not be higher than 105% of the rated voltage of the operating tap. For special use cases (for example, the active power of the transformer can flow in any direction), it is allowed to operate at a rated voltage not exceeding 110%. If there is no special requirement for the relationship between current and voltage, when the load current is K of the rated current (K cluster 1) times, limit the voltage U according to the following formula (1) The multiples and time allowed for overvoltage operation of shunt reactors, arc suppression coils, voltage regulators and other equipment, according to the manufacturers regulations.

4.1.2 When the non-excitation voltage regulating transformer changes the tap position within the range of rated voltage ± 5%, its rated capacity remains unchanged. If it is a 7.5% and a 10% tap, its capacity should be according to the manufacturer regulations; if there is no manufacturers regulations, the capacity should be reduced by 2.5% and 5% accordingly. The capacity of each tap position of the on-load voltage regulating transformer shall be specified by the manufacturer.

4.1.3 The oil temperature of the top layer of the oil-immersed transformer should generally not exceed the regulations in Table 1 (if the manufacturer has regulations, the manufacturer must stipulate). When the cooling medium temperature is lower, the top oil temperature also decreases accordingly. Generally, the oil temperature of the top layer of the Bairan circulating cooling transformer should not exceed 85 ℃ frequently.

Do a good job in the operation procedures of power transformers, so that we can reduce the occurrence of errors in use, thereby improving the efficiency of operation, and deal with using principles in later use.